There are known arrangements where the piston holds a simple revolving motion. It is eccentrically placed inside the circular covering equipped by the extension seals, which fill changing distances between the piston and the circular covering and concurrently enclose changing workspaces between the piston and the cylinder covering. This arrangement does not tolerate high pressure or temperature therefore it can only be used as a blower. Furthermore, there are known arrangements where the piston holds one compound revolving motion i.e. rolling motion (by rolling a bigger circle, for example the central circle of the inside tooth-wheel, over an immobile smaller circle for example the central circle of the tooth-wheel with an internal gearing, by means of the tooth-wheels). The diameters ratio of both circles quantifies the number of the piston cusps, which follows the same curve and also the same number of workspaces enclosed by the piston. If the ratio is 2:1, the piston has two cusps and encloses two workspaces. If the ratio is 3:2, the piston has three cusps and encloses three workspaces etc. At the higher number than two of the piston cusps, the covering curve has very inconvenient shape for a combustion space and in addition the biggest-the smallest volume ratio of the workspace is principally restricted, which is the disadvantage of this solution. Two cusps arrangement can else provide more convenient combustion space and more convenient the biggest-the smallest workspace ratio, but also principally gives the adverse ratio of piston surface encumbered by work pressure to the biggest possible critical shaft diameter, which the piston is embedded on. This arrangement is therefore not suitable for engines, but only for blowers or pumps and low work pressure compressors.
There is another known concept of the piston with two cusps motion, where both of the cusps follow a curve called conchoid. In this concept, the piston is embedded in a sliding way on two parallel shafts normal to their revolving axes. Herewith, the piston sliding motion toward the individual shafts are mutually perpendicular. One of these shafts acts as a supporting shaft and the other as a conducting shaft; herewith both of them are always embedded just in one sidewall. One of them is adapted in a tubular jig way, which passes through the other shaft, in order to embed both of them into both sidewalls.
According to other known concepts one of the shafts can be replaced by one or by number of pivots protruding from the piston is embedded on, can also be replaced (in other concepts) by the shaft with the crank pivot, which the piston is embedded on, herewith the conducting shaft, as mentioned above, is replaced by the pivots. These conchoid concepts also have common disadvantages such as, insufficient bearing capacity of the supporting shaft and an inaccurate piston guide sensitive to wear. These construction concepts have not therefore been seen and stayed in the conception state even though they have been well known since the beginning of the 20th century,